A STUDY ON A CUCKOO SEARCH BASED CO-ORDINATION OF DISTRIBUTED GENERATION UNITS AND SHUNT CAPACITOR BANK IN RADIAL DISTRIBUTION NETWORKS

CHAPTER ONE

INTRODUCTION

1.1 Background of Study

Electrical power systems are evolving from the conventional power systems known, where generation plants are connected to a distribution or transmission network to new trends involving decentralized systems consisting of small generating units connected directly to a distribution system near demand consumption. This type of generating unit is termed Distributed Generation (DG) (Pepermanset al., 2005). Among various DG types, the renewable energy (Micro- DG) units are becoming more common since majority of other DG resources (power electronic and synchronous generator based DG units) are capable of injecting harmonics to the network and are not environmentally friendly. A capacitor bank is another device that can be directly connected to a distribution network to provide a proper balance between active and reactive power injection and consumption. Among the types of capacitor banks, the shunt compensating capacitor bank is mostly suitable for distribution networks because of its ability to inject as well as absorb reactive power when needed thereby protecting against low power factor associated with network loads that leads to power losses, voltage drops and voltage instability.

Distribution system is a network that provides a final link between the high voltage transmission system and the consumers. In distribution system, among the various network topologies, the radial network topology is common because of its simplicity. The challenges of radial distribution system include; high power losses, voltage drops, transients and harmonic distortion on the distribution networks (Ogunyemi and Adejumobi, 2012). Solving these power quality problems using conventional solutions such as distribution network expansions and substation upgrades are more capitally incentive and requires years of planning and implementation. The adverse effects of harmonic injection and low power factor in power systems include the accumulation of zero sequence current in the neutral line causing overheating of the neutral cable, overheating of transformers and power system equipments, additional losses and voltage instability. This therefore provides a motivation to select a Distributed Generation and shunt capacitor bank (Heydari et al, 2013).

Distribution networks are mostly radial in nature with very rare exceptions, with the customers having one source of supply. A typical distribution network consists of distribution substation, feeders, switches, fuses, transformers, voltage regulators, meters and circuit breakers as shown in Figure 1.1